Scientists find clue to why mitochondrial DNA comes only from mom | Science News

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Scientists find clue to why mitochondrial DNA comes only from mom

Protein destroys contribution from dad’s sperm, study in worms shows

By
2:00pm, June 23, 2016
cell and fertilized egg with mitochondria

BREAK DOWN  Like most cells, sperm contain energy-producing mitochondria (one organelle and its membrane (red circle) shown, left). Once a sperm fertilizes an egg, the sperm’s mitochondria break down inside that membrane (right).

Scientists have found a clue to why one type of DNA is passed down to children by their mothers — but not their fathers.

DNA inside energy-producing organelles called mitochondria is destroyed in a dad’s sperm shortly after it fertilizes an egg, researchers report online June 23 in Science. A protein called CPS-6 cuts apart the mitochondrial DNA in the male sperm so that the DNA can’t make the proteins that the mitochondria need to power the cell. Lingering paternal mitochondrial DNA might hurt developing embryos, the researchers say.

“This is a very long-standing mystery in biology — why in so many organisms, [only] the maternal mitochondria are inherited,” says Ding Xue, a geneticist at the University of Colorado Boulder who led the work.

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